The invention relates to an apparatus for determining mass flows according to the Coriolis principle, as well as to an advantageous construction of this apparatus as an automatic mass dosing machine.
Such apparatuses are e.g. used in production and testing installations in the chemical and pharmaceutical industries, as well as the plastics, beverages, food, feed and paper industries. Another field of use is research in industry and Universities.
Dosing apparatuses for liquids are commercially available in the most varied forms. For example, dosing pumps are known, which in a first working stroke fill a given volume with the liquid to be dosed and then eject said volume in the following stroke. In addition, dosing apparatuses are known, which can be based on a mechanical volumetric meter, which can e.g. be an oval wheel meter or counter or a turbine, operated in a plant equipped with additional regulating and control means. In order to obtain with the aid of the known dosing apparatuses both precise and long term-stable results, it is necessary to standardize the volume to be measured to reference temperature, density and viscosity values. This requires complicated measuring and calculating means. Further disadvantages relate to mechanical wear between moving parts, high maintenance costs with frequent replacement of parts, no constant, but instead a pulsating measuring material flow, as well as the impediment thereof, e.g. by the pipe cross-section. Finally, the known dosing apparatuses are relatively expensive.
It is also known for the purpose of dosing liquids to use balances (Weinberg, H.: Gemenge- und Dosiertechnologie, Expert Verlag GmbH 1989). Such dosing apparatuses suffer from the serious disadvantage that the mass of the measuring material in the case of a fluid can only be determined discontinuously, i.e. by interrupting the mass flow.
Finally mass flow determination apparatuses of the aforementioned type are known, i.e. those which utilize the Coriolis acceleration as the measuring principle for the flow measurement. Such apparatuses are e.g. known from U.S. Pat. Nos. 2,624,198 and 3,355,944. Although these known apparatuses permit a continuous determination of the mass flow, they can only be used to a limited extent as dosing apparatuses and even then involve a relatively high additional regulating and control effort and expenditure. Another serious disadvantage of mass flow determination apparatuses based on the Coriolis principle is that this measuring principle is very sensitive to the coupling in of vibrations from the outside and the coupling out of vibrations into the process pipe. The coupling in of vibrations or vibration leaks lead to a varying degree of falsification of the measured values. It must be borne in mind that the sensor of the apparatus is unable to distinguish between planned vibrations supplied to the measuring pipe by apparatus-internal vibration generators and vibrations introduced from the outside. In addition, vibration leaks or losses cannot be detected by the sensor.